Dorothy FarrarOvarialfollikel
The unit consisting of the female egg cell (oocyte), follicular epithelial cells and two layers of connective tissue is called the ovarian follicle . The maturation of the ovarian follicle occurs in the woman’s ovary. When the follicle is fully mature, ovulation occurs. The maturation process is primarily controlled by the follicle-stimulating hormone (FSH).
Definition
The ovarian follicle is also known as the egg sac. The most important part of the ovarian follicle is the egg cell. The ovum is the female germ cell and contains all of the female genetic makeup. In the ovarian follicle, this egg cell is surrounded by so-called follicular epithelial cells, also known as granulosa cells.
They protect the egg cell and help it mature. Due to their function, the follicular epithelial cells are also referred to as auxiliary cells. Ovum and auxiliary cells are protected by two layers of connective tissue, the inner theca interna and the outer theca externa.
Anatomy and function
The ovarian follicle serves one purpose, reproduction. In order for the necessary ovulation to occur, the follicle goes through various stages and ensures that the egg cell matures sufficiently.
Even before birth, the ovum (oogonium) of the female unborn child divides into primary ooocytes. Although these oocytes have already entered the first meiotic division, [[meiosis], they do not complete this division. The primary oocytes are now surrounded by follicular epithelial cells. From this point on, one speaks of the primordial follicle.
At the time of birth, each ovary contains about 400,000 of these primordial follicles. The follicles remain in this intermediate stage for many years. Only with the onset of puberty do the follicles continue to differentiate in a monthly cycle. This differentiation is controlled by the release of follicle stimulating hormone (FSH) from the pituitary gland .
About ten to twenty primordial follicles mature into primary follicles in each cycle. The epithelium of the primary follicles is more pronounced than that of the predecessor follicles. The egg in the follicle begins to grow. The follicular epithelium becomes multilayered and the layers of connective tissue are formed.
At this stage, the ovarian follicle is also known as the secondary follicle. In the next stage, a follicular cavity is formed. This is filled with liquid. The oocyte is now embedded in a cluster of granulosa cells. This hill is also called egg hill. At this point in time, a differentiation into the outer and inner layers of connective tissue also takes place. This is the stage of the tertiary follicle. Androgens are formed in the connective tissue layer of the ovarian follicles.
These are converted to estrogen in the granulosa cells . Under the hormonal influence, the ovarian follicle grows and becomes the Graafian follicle. This follicle is ready to rupture. Ovulation occurs when the connective tissue cells of the follicle produce a lot of estrogen.
This increase in estrogen triggers the release of luteinizing hormone (LH) in the pituitary gland. This in turn causes ovulation. During ovulation, the mature egg cell is pushed out of the ovarian follicle and taken directly into the fallopian tube.
After ovulation, the corpus luteum is formed from the remainder of the follicle. This produces progesterone. Progesterone prevents the uterine lining from breaking down and menstruation from occurring. If the egg cell is fertilized, it produces the hormone HCG. This continues to stimulate the corpus luteum so that the fertilized egg cell can implant itself in the lining of the uterus.
If fertilization does not occur, the corpus luteum degrades after about ten days. Progesterone production stops and the lining of the uterus breaks down. Menstruation occurs.
Diseases
- Follicle atraction
- Polyzystisches Ovarialsyndrom
- follicular cysts
The destruction or regression of ovarian follicles is referred to as follicular atrasia. Ovulation is no longer possible with such follicles. Follicular atrasia can occur at any follicular stage and is, to some extent, a normal process. Of the 400,000 follicles created, only about 300 to 500 follicles develop to the point of fertilization.
In PCO syndrome, the polycystic ovary syndrome, there is an increased tendency to follicular atresia. Patients with PCO syndrome suffer from an increased production of luteinizing hormone (LH). This causes the granulosa cells to die, which in turn means that fewer androgens, i.e. male sex hormones, can be converted into estrogens.
Male hormones in the blood are often elevated in PCO patients. Polycystic ovarian syndrome is one of the most common causes of menstrual disorders and infertility in women.
Disturbed hormonal regulation mechanisms can lead to the formation of follicular cysts in the ovary. They develop when the follicle does not open during ovulation and releases the egg cell, but remains closed. Over time, this follicular cyst gets bigger and bigger.
The cells of the follicle continue to produce estrogen. This leads to menstrual disorders in the affected patients and possibly also to changes in the lining of the uterus. Sometimes there is slight unilateral pain in the lower abdomen . However, patients with follicular cysts can also be completely symptom-free.
All cysts are at risk of rupture or stalk rotation. Both complications result in acute and severe abdominal pain. Surgical removal of the entire ovary is then often required.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.